st: Granger Causality Test after regress different from vargranger

When testing for Granger Causality I get slightly different p-values
when using a regress and test command (approach1) as opposed to using a
var and vargranger command (approach2). Are these two approaches
identical as the Time Series Manuals suggests or is there a theoretical
difference between the two? If yes, which one would be preferrable in a
single equation framework?